Development of High Early Strength Concrete Using Indeginious Materials

Abstract

For accelerated production of concrete, while maintaining durability, High Early Strength (HES) concrete is increasingly finding its use in construction industry worldwide. However, its use in Pakistan is limited due to higher cost. The high cost effect is due to the constituents i.e. high quantity of cement and use of costly imported accelerating admixtures, like calcium chloride and calcium nitrite. This research work was designed to develop HES concrete, using indigenous materials and chloride and non- chloride based accelerators. The research was conducted in two phases. In first stage, trial mixes were prepared by varying the quantities of variables (cement content, accelerator type, accelerator dosage, superplasticizer dosage, air-entraining admixture dosage, and water/cement ratio). The concrete specimens were tested to evaluate the 24 hour compressive strength for the development of final design mixes. In the second phase, various tests were conducted on the concrete prepared with design mixes finalized in phase one and a comparison of these tests were drawn. The comparison of test results revealed, that concrete prepared with locally available admixture (sodium carbonate) conformed to specifications and were well with in the range. Sodium carbonate was found more effective than calcium nitrate (non-chloride based), and the quantity used was 3.5 times lesser than calcium nitrate. Comparative cost analysis indicated that HES concrete prepared with sodium carbonate is approximately 3.5 times cheaper than concrete prepared with imported accelerators (calcium chloride and calcium nitrate).